Method and system to detect packets of different formats in a receiver

Abstract

A method and system of communicating packets and detecting packets are disclosed. In a first aspect, the method and system comprise enabling the detection of a very high throughput (VHT) signal field. The VHT signal field is distinguishable from other signal fields, wherein the VHT signal field allows for a backward compatibility with other devices. In a second aspect, the method and system comprise initializing the device to be in receive mode and receiving at least one signal field symbol and detecting the presence of additional signal field symbols. The method and system further include distinguishing a very high throughput (VHT) signal field from other signal field symbols and decoding the VHT signal field parameters uniquely describing the VHT packet format.

1 . A method of communicating packets of different formats in a transmitter, the method comprising;
 enabling the detection of a very high throughput (VHT) signal field wherein the VHT signal field is distinguishable from other signal fields; and   applying a predetermined degree rotation to all of VHT signal field subcarriers after modulating the subcarrier with alternating predetermined degree shifts, wherein the VHT signal field allows for a backward compatibility with other devices.   
     
     
         2 . The method of  claim 1  whereby the transmitter transmits at least one signal field symbol and is capable of transmitting a plurality of 802.11 signal fields, the plurality of 802.11 signal fields including the VHT signal field. 
     
     
         3 . The method of  claim 1  wherein the BPSK rotation is on alternating subcarriers. 
     
     
         4 . The method of  claim 3  wherein the alternating subcarriers are odd and even. 
     
     
         5 . The method of  claim 3  wherein the BPSK symbols comprise a real and an imaginary component. 
     
     
         6 . The method of  claim 1  wherein the predetermined degree rotation comprises a 45 degree rotation and the predetermined degree shift comprise 0, 90 degree shifts. 
     
     
         7 . A method for detecting packets of different formats in a receiver comprising:
 initializing the device to be in receive mode;   receiving at least one signal field symbol;   detecting the presence of additional signal field symbols;   distinguishing a very high throughput (VHT) signal field from other signal field symbols;   decoding the VHT signal field parameters uniquely describing the VHT packet format; and   applying a predetermined reversed angular rotation to all of VHT signal field subcarriers after demodulating the subcarrier with alternating predetermined degree shifts.   
     
     
         8 . The method of  claim 7  wherein the detection comprises summing a difference in power between real and imaginary components of the symbol. 
     
     
         9 . The method of  claim 8  wherein summing the difference comprises a summation wherein the summation comprises: 
       
         
           
             
               
                 
                   
                     
                         
                     
                     ∑ 
                   
                   
                     
                         
                     
                      
                     
                       i 
                       , 
                       even 
                     
                   
                   
                     
                         
                     
                      
                     Nsc 
                   
                 
                  
                 
                   ( 
                   
                     
                       I 
                       i 
                       2 
                     
                     - 
                     
                       Q 
                       i 
                       2 
                     
                   
                   ) 
                 
               
               - 
               
                 
                   ∑ 
                   
                     k 
                     , 
                     odd 
                   
                   Nsc 
                 
                  
                 
                   ( 
                   
                     
                       I 
                       k 
                       2 
                     
                     - 
                     
                       Q 
                       k 
                       2 
                     
                   
                   ) 
                 
               
             
           
         
       
     
     
         10 . The method of  claim 9  wherein the summation is over even and odd subcarriers. 
     
     
         11 . The method of  claim 7  wherein the predetermined reversed angular rotation comprises a −45 degree rotation and the predetermined degree shifts comprise 0, 90 degree shifts. 
     
     
         12 . A system for communicating packets of different formats in a transmitter, the packet comprising a signal field, the system comprising:
 means for enabling the detection of a very high throughput (VHT) signal field wherein the VHT signal field is distinguishable from other signal fields; and   means for applying a predetermined reversed angular rotation to all of VHT signal field subcarriers after demodulating the subcarrier with alternating predetermined degree shifts, wherein the VHT signal field allows for a backward compatibility other devices.   
     
     
         13 . The system of  claim 12  wherein the BPSK symbols are on alternating subcarriers. 
     
     
         14 . The system of  claim 13  wherein the alternating subcarriers are odd and even. 
     
     
         15 . The system of  claim 13  wherein the BPSK symbols comprise a real and an imaginary component. 
     
     
         16 . The system of  claim 15  wherein the detection comprises summing a difference in power between the real and imaginary components. 
     
     
         17 . The system of  claim 16  wherein the imaginary components are large relative to the real components if the data packet comprises a 90 degree BPSK symbol. 
     
     
         18 . The system of  claim 16  wherein summing the difference comprises a summation wherein the summation comprises: 
       
         
           
             
               
                 
                   
                     
                         
                     
                     ∑ 
                   
                   
                     
                         
                     
                      
                     
                       i 
                       , 
                       even 
                     
                   
                   
                     
                         
                     
                      
                     Nsc 
                   
                 
                  
                 
                   ( 
                   
                     
                       I 
                       i 
                       2 
                     
                     - 
                     
                       Q 
                       i 
                       2 
                     
                   
                   ) 
                 
               
               - 
               
                 
                   ∑ 
                   
                     k 
                     , 
                     odd 
                   
                   Nsc 
                 
                  
                 
                   ( 
                   
                     
                       I 
                       k 
                       2 
                     
                     - 
                     
                       Q 
                       k 
                       2 
                     
                   
                   ) 
                 
               
             
           
         
       
     
     
         19 . The system of  claim 18  wherein the summation is over even and odd subcarriers. 
     
     
         20 . The system of  claim 12  wherein the predetermined reversed angular rotation comprises a −45 degree rotation and the predetermined degree shifts comprise 0, 90 degree shifts.